Using raw access on device /dev/lirc0
Problems: this device is not a LIRC kernel device (it does not
support LIRC_GET_REC_MODE ioctl). This is not necessarily a
problem, but mode2 will not work. If you are using the --raw
option you might try using without it and select a driver
instead. Otherwise, try using lircd + irw to view the decoded
data - this might very well work even if mode2 doesn't.

I am new to the PI world, I don’t know where the problem is. The receiver? The circuit? Pins? Please help !

@Teofil Sandu, I skimmed through the tutorial hackster.io/austin-stanton/… to see if you missed anything in your installation procedure. Now I am scribbling something and hopefully can make an answer. I am going very slow because I am also a lirc newbie and have not tried this lirc thing before. – tlfong011 hour ago

@Teofil Sandu, Now I have summarized the installation and testing procedure in Appendix A of my answer. The tutorial is a bit out of date. I worried that the driver or kernel is not compatible with your Rpi3B+ raspbian 9 stretch (let me know if my guess of your config is correct). The tutorial also suggests to read the LIRC user guide. I have never read this guide. So I need to first skim through it, to understand what the hell is “Mode 2”, and should I indeed to use Mode2. – tlfong011 hour ago

@Teofil Sandu, Now I have googled the LIRC wikipedia but found it too brief. But at least now know what does “LIRC” stands for (See Appendix B). I need to google further to learn more. – tlfong0155 mins ago

I remember some weeks ago I was playing with a HDMI switcher which uses infra red control. So I bought some IR toys to DIT remotes. I was thinking of remotes by hand. But now on second though perhaps I should consider using Rpi LIRC to control those remotes instead by my stupid human hand. So I am visiting the post to refresh my memory. raspberrypi.stackexchange.com/questions/99823/… – tlfong0124 mins ago

@Teofil Sandu, my old answer to the HDMI switcher question includes some references of IR emitter and detector. I found one instructable very good. I have included it in my answer – Reference 4. There is a detailed description on how to install and test LIRC (Steps 23~25). Now I am taking a break and carry on tomorrow. You might like to comment on my progress so far. – tlfong01just now Edit

***Materials***
(1) Raspberry Pi 2
(2) 940nm IR LED 40deg - 40 degree viewing angle. Bright and tuned to 940nm wavelength.
(3) 38khz IR Receiver - Receives IR signals at remote control frequencies
(4) PN2222 Transistor - Transistor to help drive IR LED
(5) 10k Ohm resistor - Resistor that goes between RPI GPIO and the PN2222 transistor
***Installation***
sudo apt-get install lirc
Add to your /etc/modules file by entering the command below:
sudo cat >> /etc/modules <<EOF
lirc_dev
lirc_rpi gpio_in_pin=23 gpio_out_pin=22
sudo cat > /etc/lirc/hardware.conf <<EOF
# /etc/lirc/hardware.conf
# Arguments which will be used when launching lircd
LIRCD_ARGS="--uinput"
# Don't start lircmd even if there seems to be a good config file
# START_LIRCMD=false
# Don't start irexec, even if a good config file seems to exist.
# START_IREXEC=false
# Try to load appropriate kernel modules
LOAD_MODULES=true
# Run "lircd --driver=help" for a list of supported drivers.
DRIVER="default"
# usually /dev/lirc0 is the correct setting for systems using udev
DEVICE="/dev/lirc0"
MODULES="lirc_rpi"
# Default configuration files for your hardware if any
LIRCD_CONF=""
LIRCMD_CONF=""
########################################################
EOF
Edit your /boot/config.txt by entering the command below:
cat >> /boot/config.txt <<EOF
dtoverlay=lirc-rpi,gpio_in_pin=23,gpio_out_pin=22
EOF
Now restart lircd so it picks up these changes:
sudo /etc/init.d/lirc stop
sudo /etc/init.d/lirc start
***Testing the IR Receiver***
Testing the IR receiver is relatively straightforward. Run these two commands to stop lircd and start outputting raw data from the IR receiver:
sudo /etc/init.d/lirc stop
mode2 -d /dev/lirc0
Point a remote control at your IR receiver and press some buttons. You should see something like this:
space 16300
pulse 95
space 28794
pulse 80
space 19395
pulse 83
space 402351
pulse 135
space 7085
pulse 85
space 2903
If you don’t, something is probably incorrectly configured. Triple check that you’ve connected everything properly and haven’t crossed any wires. I highly recommend referring to the schematics I linked to above. There is also some trouble shooting advice in the RaspberryPi Forum thread I linked to above. Finally - you may want to do this in a dark room. I found that my desk lamp and overhead light would cause the IR receiver to think it was receiving valid signals.
***Testing the IR LED***
You’re going to need to either find an existing LIRC config file for your remote control or use your IR receiver to generate a new LIRC config file(find existing remote profiles here). In my case, I created a new LIRC config file. To do this, read the documentation on the irrecord application that comes with LIRC.
When using irrecord it will ask you to name the buttons you’re programming as you program them. Be sure to run irrecord --list-namespace to see the valid names before you begin.
Here were the commands that I ran to generate a remote configuration file:
# Stop lirc to free up /dev/lirc0
sudo /etc/init.d/lirc stop
# Create a new remote control configuration file (using /dev/lirc0) and save the output to ~/lircd.conf
irrecord -d /dev/lirc0 ~/lircd.conf
# Make a backup of the original lircd.conf file
sudo mv /etc/lirc/lircd.conf /etc/lirc/lircd_original.conf
# Copy over your new configuration file
sudo cp ~/lircd.conf /etc/lirc/lircd.conf
# Start up lirc again
sudo /etc/init.d/lirc start
Once you’ve completed a remote configuration file and saved/added it to /etc/lirc/lircd.conf you can try testing the IR LED. We’ll be using the irsend application that comes with LIRC to facilitate sending commands. You’ll definitely want to check out the documentation to learn more about the options irsend has.
Here are the commands I ran to test my IR LED (using the “Roku” remote configuration file I created):
# List all of the commands that LIRC knows for 'Roku'
irsend LIST Roku ""
# Send the KEY_POWER command once
irsend SEND_ONCE Roku KEY_POWER
# Send the KEY_VOLUMEDOWN command once
irsend SEND_ONCE Roku KEY_VOLUMEDOWN
I tested that this was working by pointing the IR led at my Roku receiver and testing whether I could turn it on and press enter.
sudo cat > /etc/lirc/hardware.conf <<EOF
# /etc/lirc/hardware.conf
# Arguments which will be used when launching lircd
LIRCD_ARGS="--uinput"
# Don't start lircmd even if there seems to be a good config file
# START_LIRCMD=false
# Don't start irexec, even if a good config file seems to exist.
# START_IREXEC=false
# Try to load appropriate kernel modules
LOAD_MODULES=true
# Run "lircd --driver=help" for a list of supported drivers.
DRIVER="default"
# usually /dev/lirc0 is the correct setting for systems using udev
DEVICE="/dev/lirc0"
MODULES="lirc_rpi"
# Default configuration files for your hardware if any
LIRCD_CONF=""
LIRCMD_CONF=""
EOF

LIRC (Linux Infrared Remote Control) is an open source package that allows users to receive and send infrared signals with a Linux-based computer system. With LIRC and an IR receiver the user can control their computer with almost any infrared remote control (e.g. a TV remote control). The user may for instance control DVD or music playback with their remote control.

However, LIRC offers more flexibility and functionality and is still the right tool in a lot of scenarios. The most important part of LIRC is the lircd daemon which decodes IR signals received by the device drivers and provides the information on a socket. It also accepts commands for IR signals to be sent if the hardware supports this.

The user space applications allows you to control your computer with your remote control. You can send X11 events to applications, start programs and much more on just one button press.

There are some config files for remote controls at the remotes database. This is about 2500 devices and counting. These devices should work with the general drivers or (if it lacks timing info) the driver used to create them.

If you can’t find your remote control here it does not mean that your remote control is not supported. It’s just that there is no config file for it yet.

All remote controls that are supported by learning remote controls i.e., almost any, should also work with LIRC.

Supported capture devices

Besides a remote control you also need a capture device to read the data from the remote.

Former versions focused on home-brew capture hardware connected to the serial or parallel port. Descriptions how to build such hardware can be found here. Current versions of LIRC also support a broad range of other hardware.

As a starter, you can use the kernel built-in support for many USB dongles and similar. Besides this LIRC supports basically any conceivable way to capture your data including serial devices, parallel ports, sound input etc. You can see the complete list in the left pane.